1. Field of the Invention
This invention can be used in mechanical engineering, instrument making and other fields in which hard brittle materials are machined. The invention is designated for ultrasonic dimensional treatment of workpieces of, for example, monocrystals such as celesium, quartz, chromium and germanium, and polycrystals such as ceramics.
2. Description of the Related Art
At modern development of mechanical engineering, high quality and productivity of ultrasonic dimensional treatment (UDT) processes of workpieces can be achieved with usage of special mechanisms (changing mechanisms) for tool displacement relative to the workpiece and also with special service systems which take into account peculiarities of treatment of particular workpieces. Clamping mechanisms are designated for creating a necessary pressure between the tool and the workpiece and also for supporting the tool during a cutting process.
Ultrasonic machines having clamping mechanisms with balancing weights were the first ultrasonic machines to be used in which a clamping force was provided due to a weight difference between an acoustic head and a weight suspended on a flexible band thrown over a pulley system or supported on a lever. Such a system is sometimes used for applying a clamping force between the workpiece and the tool. Change of the force is obtained by replaceable weights or by displacing the weights along a lever. (cf. U.S. Pat. No. 2,580,716, Rosenberg L.D. et al. "Ultrasonic cutting", Moscow, U.S.S.R., Academy of Sciences, 1961, p. 159).
Due to gross inertia and considerable frictional forces of the force transfer system, these and similar ultrasonic machines do not possess sufficient dynamic range of clamping force change and sufficiently small increments, both of which are required for treatment of small workpiece of monocrystal type.
Known in the art are ultrasonic machines manufactured by foreign firms and provided with clamping mechanisms which use balancing springs (cf. Margolin V.S. et al. "Ultrasonic machines" (Survey of foreign structures), ZINTIAM, M. 1963, p. 40). Their advantages are compactness and sufficiently high sensitivity. They are characterized, however, by an unstable clamping force and also by impossibility to regulate the force according to a program and in a wide range.
A number of machines manufactured abroad use a clamp regulator with an electric motor to be periodically switched on (cf. U.S. Pat. No. 2,942,383). The electric motor shifts off, through a worm gearing, the spring balancing the acoustic head, the clamping force being equal to the difference between a head weight and the spring clamping force. Contacts are provided to be moved together with a sliding nut (which is displaced when rotating a screw through the worm gearing). The contacts, when abutting a stop on the acoustic head break an electrical circuit. During the treatment, the acoustic head cuts into the workpiece goes down, and the contacts are opened.
Due to usage of the spring mechanisms, however, the sensitivity is not uniform and is insufficient for practical purposes of crystal treatment.
A more perfect installation scheme was used in the first prototype of the ultrasonic machine model 4772 which was shown on Brussel's exhibition in 1958. An inductance-type transducer was used instead of contacts although the disadvantages for the given treatment remained the same.
Known also in the art are ultrasonic machines with clamping mechanism of the solenoid type (cf. U.S.S.R. Inventor's Certificate No. 114937, and Livshitz A.L. et al. "Universal ultrasonic machine model 4772", "Machines and tools", 1959, No. 6, pp. 10-12) in which the clamping force of these mechanisms is regulated by a rod of a solenoid, a core of which is a counterweight or its slider.
The disadvantage of the machines using the solenoid is low sensitivity and nonlinearity of the force along the whole running path.
Known in the art is the clamping mechanism of the ultrasonic machine with the regulator of the clamping force using an electric motor which operates in a braked mode (cf. U.S.S.R. Inventor's Certificate No. 117882, publ. in 1957). A synchronous servomotor, through a gear reducer and a rack-and-gear drive, actuates a slider supporting the acoustic head. The motor operates in such mode that the motor, being stopped, continues to develop a torque and, therefore, the clamping force which presses a tool to the workpiece (the motor acts as a wound-up spiral spring).
However, due to presence of considerable frictional forces, this clamping system has low sensitivity in respect of the clamping force.
Ultrasonic machine model 46772 is the closest prior art apparatus in respect of the claimed technical essence and the achieved result. In said machine a spindle is balanced by a counterweight and a rocker in such a way that a surplus weight remains of the order 5-6.5 kg (cf. Markov A.I. "Ultrasonic cutting of hard-to-machine materials", Moscow, U.S.S.R., "Mechanical engineering", 1968, pp. 81, 387). The counterweight moves along the rocker which compensates for the surplus weight.
The given machine, however, has low sensitivity of the clamping mechanism and of the setting of the clamping force by reason of considerable frictional forces in the mechanism and inertiality of a mechanical system, narrow range of regulation (about 40:1) stipulated by a structure embodiment and is characterized by complexity of automation of UDT process, and low productivity.